#!/bin/bash

# ssh config
IDENTITY="/root/.ssh/id_rsa"
SSH_SOCKET="/run/ssh-tunnel.sock"
SSH_USER="root"
# network config
LOCAL_IP="10.0.0.2"
PORTS="5432 20 21 10090:10100"
REMOTE_IP="10.0.0.1"
REMOTE_EXTIP="185.82.216.108"
REMOTE_EXTIF="eth0"
# daemon
SLEEPTIME="5m"
# notifications
FROM="server@repo.arcanis.name"
TO="darkarcanis@mail.ru"
SUBJECT="Server status report"
# cmds
IFCFG="/sbin/ifconfig"
IPT="/sbin/iptables"
MAIL="/usr/bin/mail"
SSH="/usr/bin/ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null \
                  -o TCPKeepAlive=yes -o ServerAliveInterval=600 -o ServerAliveCountMax=360 \
                  -o ControlMaster=auto -o PasswordAuthentication=no -i ${IDENTITY} "


function send_mail() {
  local MESSAGE="${1}"

  echo "${MESSAGE}" | "${MAIL}" -r "${FROM}" -s "${SUBJECT}" "${TO}"
}

function do_start() {
  [ -e "${SSH_SOCKET}" ] && rm -f "${SSH_SOCKET}"
  ${SSH} -M -S "${SSH_SOCKET}" -f -w 0:0 "${SSH_USER}"@"${REMOTE_EXTIP}" \
          "${IFCFG}" tun0 "${REMOTE_IP}"/30 pointopoint "${LOCAL_IP}"
  "${IFCFG}" tun0 "${LOCAL_IP}"/30 pointopoint "${REMOTE_IP}"

#  send_mail "Tunnel has been started"
}

function do_stop() {
  ${SSH} -S "${SSH_SOCKET}" -O exit "${SSH_USER}"@"${REMOTE_EXTIP}"
  [ -e "${SSH_SOCKET}" ] && rm -f "${SSH_SOCKET}"

# send_mail "Tunnel has been stoped"
}

function do_table() {
  local PORT="${1}"

  ${SSH} "${SSH_USER}"@"${REMOTE_EXTIP}" \
         "${IPT}" -t nat -A PREROUTING --dst "${REMOTE_EXTIP}" -p tcp --dport "${PORT}" -j DNAT --to-destination "${LOCAL_IP}"
  ${SSH} "${SSH_USER}"@"${REMOTE_EXTIP}" \
         "${IPT}" -t nat -A POSTROUTING --dst "${LOCAL_IP}" -p tcp --dport "${PORT}" -j SNAT --to-source "${REMOTE_IP}"
  ${SSH} "${SSH_USER}"@"${REMOTE_EXTIP}" \
         "${IPT}" -t nat -A OUTPUT --dst "${REMOTE_EXTIP}" -p tcp --dport "${PORT}" -j DNAT --to-destination "${LOCAL_IP}"
  ${SSH} "${SSH_USER}"@"${REMOTE_EXTIP}" \
         "${IPT}" -I FORWARD 1 -i "${REMOTE_EXTIF}" -o tun0 -d "${LOCAL_IP}" -p tcp -m tcp --dport "${PORT}" -j ACCEPT
}

function do_clear_table() {
  ${SSH} "${SSH_USER}"@"${REMOTE_EXTIP}" "${IPT}" -t nat -F
  ${SSH} "${SSH_USER}"@"${REMOTE_EXTIP}" "${IPT}" -t nat -X
}

function do_add_table() {
  local PORT
  for PORT in ${PORTS}; do do_table "${PORT}"; done
}

function do_restart() {
  if do_ping; then
    do_clear_table
    do_stop
  fi
  do_start
  sleep 2
  do_add_table
}

function do_ping() {
  ping -c 4 -q "${REMOTE_IP}" &> /dev/null && return 0 || return 1
}

function do_daemon() {
  while true; do
    sleep "${SLEEPTIME}"
    echo "Check tunnel"
    if ! do_ping; then
      echo "Restart tunnel"
      do_restart
    fi
  done
}


case "${1}" in
  start)
        echo "Start tunnel"
        do_ping && exit 0
        do_start
        sleep 2
        do_add_table
        ;;
  stop)
        echo "Stop tunnel"
        do_ping || exit 0
        do_clear_table
        do_stop
        ;;
  restart)
        echo "Restart tunnel"
        if do_ping; then
          do_restart
        else
          do_start
          sleep 2
          do_add_table
        fi
        ;;
  ping)
        if do_ping; then
          echo "Active"
          exit 0
        else
          echo "Inactive"
          exit 1
        fi
        ;;
  check)
        if ! do_ping; then
          echo "Restart tunnel"
          do_restart
        fi
        ;;
  daemon)
        do_daemon
        ;;
  *)
        echo "Usage tunctl start|stop|restart|ping|check|daemon"
        exit 1
        ;;
esac

exit 0